B40.0
BillableAcute pulmonary blastomycosis
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is B40.0 an HCC code?
Yes. B40.0 maps to Pneumococcal Pneumonia, Empyema, Lung Abscess under the V24 model but is not retained in V28.
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for B40.0
For B40.0to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed B40.0 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
B40.0 is the ICD-10-CM diagnosis code for acute pulmonary blastomycosis. A fungal lung infection caused by Blastomyces that develops suddenly with acute respiratory symptoms, fever, and malaise. B40.0 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering mycoses (b35-b49).
Under the older CMS-HCC V24 model, B40.0 maps to Pneumococcal Pneumonia, Empyema, Lung Abscess (HCC 115) with a community, non-dual, aged base RAF weight of 0.339. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Acute blastomycosis typically presents within weeks of exposure to contaminated soil or water. Because B40.0 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for B40.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Acute blastomycosis typically presents within weeks of exposure to contaminated soil or water
- •Document respiratory symptoms and any systemic manifestations to support acute diagnosis
Clinical Significance
Acute pulmonary blastomycosis is an endemic mycosis caused by Blastomyces dermatitidis, prevalent in the Great Lakes region, Ohio and Mississippi River valleys, and southeastern United States. The acute form can range from mild flu-like illness to severe acute respiratory distress syndrome, making accurate documentation of acuity essential for appropriate resource allocation.
Documentation Requirements
- ✓Positive culture, histopathology, or antigen testing confirming Blastomyces
- ✓Acute symptom onset documented: fever, cough, myalgia, arthralgias
- ✓Chest imaging findings: lobar or multilobar infiltrates, mass lesions
- ✓Timeline establishing acute presentation (typically within weeks of exposure)
- ✓Exposure history to wooded, moist environments in endemic areas
Commonly Confused Codes
- •B40.1 (Chronic pulmonary blastomycosis) - chronic form shows fibrocavitary disease similar to TB; acute shows acute pneumonic infiltrates
- •B40.2 (Pulmonary blastomycosis, unspecified) - use only when acuity cannot be determined from documentation
- •J18.1 (Lobar pneumonia, unspecified organism) - blastomycosis can mimic bacterial pneumonia; fungal etiology must be coded specifically